US7912030B2 - Base station and communication system - Google Patents

Base station and communication system Download PDF

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US7912030B2
US7912030B2 US12/064,541 US6454106A US7912030B2 US 7912030 B2 US7912030 B2 US 7912030B2 US 6454106 A US6454106 A US 6454106A US 7912030 B2 US7912030 B2 US 7912030B2
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mobile station
base station
mobile
orthogonal
mobile stations
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US20090135791A1 (en
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Teruo Kawamura
Yoshihisa Kishiyama
Kenichi Higuchi
Mamoru Sawahashi
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NTT Docomo Inc
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NTT Docomo Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/08—Access point devices
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/155—Ground-based stations
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0001—Arrangements for dividing the transmission path
    • H04L5/0014—Three-dimensional division
    • H04L5/0023—Time-frequency-space
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
    • H04L5/005—Allocation of pilot signals, i.e. of signals known to the receiver of common pilots, i.e. pilots destined for multiple users or terminals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H04W56/004—Synchronisation arrangements compensating for timing error of reception due to propagation delay
    • H04W56/0045—Synchronisation arrangements compensating for timing error of reception due to propagation delay compensating for timing error by altering transmission time
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H04J13/16—Code allocation
    • H04J13/18—Allocation of orthogonal codes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0002—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate
    • H04L1/0003—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate by switching between different modulation schemes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/02—Channels characterised by the type of signal
    • H04L5/023—Multiplexing of multicarrier modulation signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/04—Wireless resource allocation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W92/00—Interfaces specially adapted for wireless communication networks
    • H04W92/04—Interfaces between hierarchically different network devices
    • H04W92/10—Interfaces between hierarchically different network devices between terminal device and access point, i.e. wireless air interface

Definitions

  • the present invention relates to a base station and a communication system which perform transmission timing control in packet access. Specifically, the present invention relates to a base station and a communication system which orthogonalize uplink signals from multiple mobile stations by controlling transmission timings of signals in packet access to be synchronized among mobile stations which are situated in multiple sectors in the same base station.
  • an increase in the system capacity be achieved by employing one-cell frequency reuse that uses the same frequency among adjacent cells.
  • gains for reducing interference from the adjacent cells are needed.
  • one-cell frequency reuse is achieved by reducing interference from the adjacent cells by means of a spreading gain obtained from spreading and a channel coding gain obtained from error correcting coding according to the principles of CDMA (Code Division Multiple Access).
  • CDMA Code Division Multiple Access
  • a further increase in the system capacity is achieved by dividing one cell into multiple areas called sectors and performing communications independently in each sector based on the principles of CDMA.
  • each mobile station can simultaneously access the base station in uplink communications from the mobile station to the base station.
  • the reason why each mobile station can simultaneously access the base station is that the base station can distinguish and demodulate (decode) signals transmitted from multiple mobile stations by means of the spreading gain, even if a collision occurs among signals transmitted from the multiple mobile stations.
  • the collision indeed occurs among signals transmitted from the multiple mobile stations when the mobile stations simultaneously access the base station.
  • the signals interfere with each other (multiple-access interference), which results in degrading communication quality.
  • the multiple-access interference occurs not only within a single cell but also among sectors. In other words, the mobile station close to a sector boundary can experience multiple-access interference in both sectors.
  • transmission timing control be performed in CDMA communications employing one-cell frequency reuse (for example, Non-Patent References 1 and 2).
  • FIG. 1 shows a schematic flowchart illustrating transmission timing control in accordance with the related art.
  • the base station BS transmits a pilot signal on a common pilot channel to two mobile stations MS 1 and MS 2 in the same sector (S 1 ).
  • the mobile stations MS 1 and MS 2 which receive the pilot signal on the common pilot channel start transmitting signals based on the reception timing of the pilot signal (S 2 ).
  • the mobile station MS 2 close to the base station receives the pilot signal earlier than the mobile station MS 1 far from the mobile station.
  • the mobile stations MS 1 and MS 2 respectively transmit signals to the base station BS according to the arrival time of the pilot signal on the common pilot channel.
  • the base station BS measures a reception timing difference between these signals (S 3 ).
  • the base station BS generates transmission timing control information based on the reception timing difference and transmits it to the mobile stations MS 1 and MS 2 (S 4 ).
  • Each mobile station starts communications based on the received transmission timing control information (S 5 ).
  • the reception timings of the signals from the mobile stations MS 1 and MS 2 are synchronized at the base station BS (S 6 ).
  • the transmission timing control allows reception timings of paths with maximum reception power for the respective mobile stations to be synchronized at the base station, and allows signals from the mobile stations to be orthogonal on the synchronized paths with maximum reception power. Accordingly, the transmission timing control can reduce multiple-access interference and improve communication quality.
  • Non-Patent Reference 1 E. Hong, S. Hwang, K. Kim, and K. Whang, “Synchronous transmission technique for the reverse link in DS-CDMA,” IEEE Trans. on Commun., vol. 47, no. 11, pp. 1632-1635, November 1999
  • the transmission timing control proposed in the Non-Patent References 1 and 2 focuses on the mobile stations with a low information rate based on circuit switching in CDMA communications. In addition, it focuses on the transmission timing control within a single sector, because reception timings of signals from many mobile stations have to be synchronized. Furthermore, Direct Sequence CDMA is used in the CDMA communications proposed in the Non-Patent References 1 and 2. Under the Direct Sequence scheme, in order for the base station to orthogonalize signals transmitted from the mobile stations, synchronization at the chip level after spreading is required, which requires transmission timing control with high accuracy.
  • the transmission timing control in accordance with the related art focuses on circuit switching based signals. Assuming that packet access is performed, the related art cannot reduce the effect of multiple-access interference to efficiently transmit signals on the pilot channel, the other control channels, or data channels, when packet scheduling or adaptive modulation is added.
  • a base station which performs transmission timing control for multiple mobile stations, including:
  • a first reception timing detecting unit configured to detect a reception timing of a packet received from a first mobile station of the multiple mobile stations which is situated in a first sector;
  • a second reception timing detecting unit configured to detect a reception timing of a packet received from a second mobile station of the multiple mobile stations which is situated in a second sector;
  • a transmission timing determining unit configured to determine transmission timings of signals transmitted from the first mobile station and the second mobile station based on the reception timings detected by the first reception timing detecting unit and the second reception timing detecting unit;
  • control information generating unit configured to generate transmission timing control information for the first mobile station and the second mobile station based on the transmission timings
  • a radio resource allocating unit configured to allocate orthogonal radio resources to the first mobile station and the second mobile station.
  • a communication system including multiple mobile stations and a base station which performs transmission timing control for the multiple mobile stations, wherein:
  • the base station includes
  • a first reception timing detecting unit configured to detect a first reception timing of a packet received from a first mobile station of the multiple mobile stations which is situated in a first sector;
  • a second reception timing detecting unit configured to detect a second reception timing of a packet received from a second mobile station of the multiple mobile stations which is situated in a second sector;
  • a transmission timing determining unit configured to determine transmission timings of signals transmitted from the first mobile station and the second mobile station based on the first reception timing and the second reception timing;
  • control information generating unit configured to generate transmission timing control information for the first mobile station and the second mobile station based on the transmission timings
  • a radio resource allocating unit configured to allocate orthogonal radio resources to the first mobile station and the second mobile station
  • the mobile station includes
  • a transmission timing adjusting unit configured to adjust a transmission timing of a signal based on the transmission timing control information.
  • the radio resource allocating unit may allocate the radio resources in consideration of a timing error within a guard interval. Allocating the radio resources in this manner allows uplink signals from multiple mobile stations to be orthogonal by means of loose (or coarse) transmission timing control within the guard interval, for example.
  • FIG. 1 shows a flowchart illustrating transmission timing control in accordance with the related art.
  • FIG. 2 shows an example of a communication system to which the present invention is applicable.
  • FIG. 3 shows a block diagram of a base station in accordance with first through third embodiments of the present invention.
  • FIG. 4 shows a flowchart illustrating transmission timing control in a base station in accordance with a first embodiment of the present invention.
  • FIG. 5 shows a diagram illustrating orthogonality in the time domain at a base station in accordance with a first embodiment of the present invention.
  • FIG. 6 shows a diagram illustrating orthogonality in the time domain at a base station in accordance with a first embodiment of the present invention.
  • FIG. 7 shows a block diagram of a mobile station communicating with a base station in accordance with a first embodiment of the present invention.
  • FIG. 8 shows a diagram illustrating orthogonality in the code domain at a base station in accordance with a second embodiment of the present invention.
  • FIG. 9 shows a block diagram of a mobile station communicating with a base station in accordance with a second embodiment of the present invention.
  • FIG. 10 shows a diagram illustrating orthogonality in the frequency domain at a base station in accordance with a third embodiment of the present invention.
  • FIG. 11 shows a block diagram of a mobile station communicating with a base station in accordance with a third embodiment of the present invention.
  • FIG. 12 shows a diagram illustrating orthogonality among multiple users (4 users) in accordance with a third embodiment of the present invention.
  • FIG. 13 shows a diagram illustrating orthogonality among multiple users (8 users) in accordance with a third embodiment of the present invention.
  • FIG. 14 shows an example of a communication system employing MIMO transmission.
  • FIG. 15 shows a block diagram of a base station in accordance with fourth through ninth embodiments of the present invention.
  • FIG. 16 shows a diagram illustrating orthogonality at a base station in accordance with the fourth embodiment of the present invention (orthogolality in the time domain among mobile stations; orthogonality in the time domain among antennas).
  • FIG. 17 shows a block diagram of a mobile station communicating with a base station in accordance with the fourth through ninth embodiments of the present invention.
  • FIG. 18 shows a diagram illustrating orthogonality at a base station in accordance with the fifth embodiment of the present invention (orthogolality in the time domain among mobile stations; orthogonality in the code domain among antennas).
  • FIG. 19 shows a diagram illustrating orthogonality at a base station in accordance with the sixth embodiment of the present invention (orthogolality in the time domain among mobile stations; orthogonality in the frequency domain among antennas).
  • FIG. 20 shows a diagram illustrating orthogonality at a base station in accordance with the seventh embodiment of the present invention (orthogolality in the code domain among mobile stations; orthogonality in the time domain among antennas).
  • FIG. 21 shows a diagram illustrating orthogonality at a base station in accordance with the eighth embodiment of the present invention (orthogolality in the code domain among mobile stations; orthogonality in the code domain among antennas).
  • FIG. 22 shows a diagram illustrating orthogonality at a base station in accordance with the ninth embodiment of the present invention (orthogolality in the code domain among mobile stations; orthogonality in the frequency domain among antennas).
  • FIG. 23 shows a diagram illustrating orthogonality at a base station in accordance with a tenth embodiment of the present invention (orthogolality in the frequency domain among mobile stations; orthogonality in the time domain among antennas).
  • FIG. 24 shows a diagram illustrating orthogonality at a base station in accordance with an eleventh embodiment of the present invention (orthogolality in the frequency domain among mobile stations; orthogonality in the code domain among antennas).
  • FIG. 25 shows a diagram illustrating orthogonality at a base station in accordance with a twelfth embodiment of the present invention (orthogolality in the frequency domain among mobile stations; orthogonality in the frequency domain among antennas).
  • FIG. 26 shows another example of a communication system to which the present invention is applicable.
  • FIG. 2 shows an example of a communication system to which the present invention is applicable.
  • the communication system includes a base station BS and mobile stations MSs.
  • the base station covers a cell with multiple sectors. Typically, each mobile station belongs to one of the sectors.
  • a mobile station # 1 MS 1 and a mobile station # 2 MS 2 belong to a sector # 1
  • a mobile station # 4 MS 4 belongs to a sector # 2 .
  • a mobile station may be situated in a sector boundary between the sector # 1 and the sector # 2 .
  • a mobile station # 3 is situated in the sector boundary. Signals transmitted from the mobile station # 3 which is situated in the sector boundary may cause interference with signals in the sectors # 1 and # 2 .
  • the base station performs transmission timing control for the respective mobile stations within all sectors to synchronize the reception timings at the base station.
  • the base station can allocate orthogonal radio resources to mobile stations within all sectors in the time, frequency, or code domain. This resource allocation can reduce multiple-access interference.
  • the present invention is applicable to orthogonalization of not only the pilot channel but also the other channels.
  • FIG. 3 shows a block diagram of a base station 10 in accordance with a first embodiment of the present invention.
  • an approach for orthogonalizing signals from respective mobile stations in the time domain is described below.
  • the base station 10 includes received signal modulation units 101 - 1 through 101 - 3 , reception timing detecting units 103 - 1 through 103 - 3 , control information generating units 107 - 1 through 107 - 3 , and transmission signal generating units 109 - 1 through 109 - 3 for sectors # 1 through # 3 , respectively.
  • the base station 10 further includes a transmission timing determining unit 105 and a radio resource allocating unit 113 .
  • the received signal modulation units 101 - 1 through 101 - 3 modulate signals received from the mobile stations.
  • the reception timing detecting units 103 - 1 through 103 - 3 detect reception timings of the received signals and provide reception timing information to the transmission timing determining unit 105 .
  • the transmission timing determining unit 105 measures a reception timing difference based on reception timing information for each mobile station within all sectors in the base station.
  • the transmission timing determining unit 105 calculates transmission timings so that signals transmitted from the respective mobile stations are synchronized within a guard interval.
  • the radio resource allocating unit 113 generates radio resource allocation information for each mobile station so that signals transmitted from the respective mobile stations are orthogonal in the time domain.
  • the control information generating units 107 - 1 through 107 - 3 generate transmission timing control information for the corresponding mobile stations based on the calculated transmission timings and the radio resource allocation information.
  • the transmission signal generating units 109 - 1 through 109 - 3 generate transmission signals for the corresponding mobile stations. The corresponding transmission signal is transmitted to each mobile station.
  • FIG. 4 shows a flowchart illustrating transmission timing control in the base station 10 shown in FIG. 3 .
  • the base station BS calculates transmission timings for respective mobile stations MS 1 and MS 2 based on signals (for example, reservation packets such as pilot signals and synchronization signals) received from the mobile stations MS 1 and MS 2 within all sectors (S 101 ). In this case, the base station BS calculates transmission timings for all mobile stations within all sectors.
  • the base station BS generates transmission timing control information based on the calculated transmission timing and transmits it to each mobile station on a downlink control channel (S 103 ).
  • Each mobile station adjust the transmission timing of a signal (on a packet data channel) based on the transmission timing control information (S 105 ). Consequently, the reception timings of signals are synchronized among the mobile stations within all sectors in the base station (S 105 ).
  • FIG. 5 shows a diagram illustrating how signals (on pilot channels) from the respective mobile stations are orthogonal at the base station in the time domain.
  • the following description focuses on orthogonalization of pilot channels, because the pilot signals (reference signals) play an important role such as measurement of the propagation path condition.
  • the present invention is also applicable to orthogonalization of the other control channels or data channels.
  • FIG. 5 shows, on the time axis, pilot channels received at the base station from the mobile stations # 1 and # 2 .
  • the pilot channel for the mobile station # 1 and the pilot channel for the mobile station # 2 do not interfere with each other on the time axis. This enables measurement of the propagation path condition with high accuracy.
  • guard intervals Cyclic Prefixes
  • CP 1 and CP 2 are taken into consideration, orthogonalization is achieved with lower accuracy of transmission timing control by ignoring interference within the guard intervals at the base station.
  • FIG. 6 shows a diagram where orthogonalization in the time domain is achieved within all sectors.
  • a signal from the mobile station # 3 close to the sector boundary is orthogonal in the time domain to signals from the mobile stations # 1 and # 2 in the sector # 1 .
  • the signal from the mobile station # 3 is orthogonal in the time domain to a signal from the mobile station # 4 in the sector # 2 . Accordingly, the signal from the mobile station # 3 close to the sector boundary does not interfere with the signals in both sectors # 1 and # 2 , and thus communication quality can be improved.
  • FIG. 7 shows a block diagram of a mobile station 20 communicating with the base station 10 .
  • the mobile station 20 includes a pilot channel generating unit 201 , a data channel generating unit 203 (as used herein, the data channel generating unit 203 includes the capability of generating a control channel), a channel multiplexing unit 205 , a scrambling code multiplying unit 207 , and a transmission timing adjusting unit 209 .
  • the channel multiplexing unit 205 multiplexes a pilot channel generated by the pilot channel generating unit 201 and a data channel generated by the data channel generating unit 203 .
  • the scrambling code multiplying unit 207 multiplies the multiplexed channel with a sector-specific or mobile-station-specific scrambling code.
  • the transmission timing adjusting unit 209 adjusts timings for transmitting signals based on transmission timing control information included in the signal from the base station so that the signals received at the base station are orthogonal in the time domain.
  • a base station 10 in accordance with the second embodiment is identical with the base station shown in FIG. 3 except that the radio resource allocating unit 113 generates code allocation information for each mobile station so that signals transmitted from the respective mobile stations are orthogonal in the code domain.
  • the transmission signal generating units 109 - 1 through 109 - 3 transmit the code allocation information to each mobile station.
  • FIG. 8 shows a diagram illustrating how signals (on pilot channels) from the respective mobile stations are orthogonal at the base station in the code domain.
  • the technology called Block-Spread CDMA Chip-Interleaved Block-Spread Code Division Multiple Access
  • Block-Spread CDMA the pilot channel for the mobile station # 1 and the pilot channel for the mobile station # 2 do not interfere with each other in the code domain. This enables measurement of the propagation path condition with high accuracy.
  • Block-Spread CDMA allows for orthogonalization with lower accuracy of transmission timing control due to guard intervals CP 1 and CP 2 .
  • CAZAC Constant Amplitude Zero Auto-Correlation codes
  • CAZAC Constant Amplitude Zero Auto-Correlation codes
  • codes can be used for orthogonalizing signals in the code domain (for example, R. L. Frank and S. A. Zadoff, “Phase shift pulse codes with good periodic correlation properties,” IEEE Trans. Inform. Theory, vol. IT-8, pp. 381-382, 1962. and D. C. Chu, “Polyphase codes with good periodic correlation properties,” IEEE Trans. Inform. Theory, vol. IT-18, pp. 531-532, July 1972.).
  • FIG. 9 shows a block diagram of a mobile station 20 communicating with the base station 10 .
  • the mobile station 20 is identical with the mobile station shown in FIG. 7 except that the pilot channel generating unit 201 receives additional input information.
  • the pilot channel generating unit 201 generates a pilot channel based on code allocation information included in the signal from the base station so that signals received at the base station are orthogonal in the code domain.
  • the pilot channel is multiplexed with a data channel, and then multiplied with a sector-specific or mobile-station-specific scrambling code.
  • the transmission timing adjusting unit 209 adjusts timings for transmitting signals based on transmission timing control information included in the signal from the base station so that the signals received at the base station are synchronized.
  • a base station 10 in accordance with the second embodiment is identical with the base station shown in FIG. 3 except for the operation in the radio resource allocating unit 113 .
  • the radio resource allocating unit 113 generates frequency allocation information for each mobile station so that signals transmitted from the respective mobile stations are orthogonal in the frequency domain.
  • the transmission signal generating units 109 - 1 through 109 - 3 transmit the frequency allocation information to each mobile station.
  • FIG. 10 shows a diagram illustrating how signals (on pilot channels) from the respective mobile stations are orthogonal at the base station in the frequency domain.
  • Distributed FDMA and Localized FDMA can be used for achieving orthogonalization in the frequency domain.
  • frequency bands are allocated to the respective mobile stations with a comb-shaped frequency spectrum.
  • the frequency spectrum in Distributed FDMA can be obtained by the technology called VSCRF-CDMA (Variable Spreading and Chip Repetition Factor-CDMA).
  • VSCRF-CDMA Very Spreading and Chip Repetition Factor-CDMA
  • the total frequency band is divided by the number of mobile stations. In either case, the pilot channel for the mobile station # 1 and the pilot channel for the mobile station # 2 do not interfere with each other in the frequency domain. This enables measurement of the propagation path condition with high accuracy. Also, when guard intervals CP 1 and CP 2 are taken into consideration, orthogonalization is achieved with lower accuracy of transmission timing control.
  • FIG. 11 shows a block diagram of a mobile station 20 communicating with the base station 10 .
  • the mobile station 20 is identical with the mobile station shown in FIG. 7 except that the pilot channel generating unit 201 receives additional input information.
  • the pilot channel generating unit 201 generates a pilot channel based on frequency allocation information included in the signal from the base station so that signals received at the base station are orthogonal in the frequency domain.
  • the pilot channel is multiplexed with a data channel, and then multiplied with a sector-specific or mobile-station-specific scrambling code.
  • the transmission timing adjusting unit 209 adjusts timings for transmitting signals based on transmission timing control information included in the signal from the base station so that the signals received at the base station are synchronized.
  • the present invention is not limited to the predetermined number of mobile stations.
  • the present invention can be applicable to orthogonalization in the frequency domain among 4 users (4 mobile stations) as shown in FIG. 12 as well as among 8 users (8 mobile stations) as shown in FIG. 13 .
  • FIG. 14 shows an example of a communication system in accordance with MIMO transmission.
  • Each mobile station # 1 , # 2 (MS 1 , MS 2 ) includes two antennas # 1 and # 2 and a base station (BS) includes two antennas # 1 and # 2 .
  • transmission timing control has to be performed to orthogonalize pilot channels from the respective antennas in addition to orthogonalizing pilot channels from the mobile stations.
  • the base station performs transmission timing control so that a signal A transmitted from the antenna # 1 in the mobile station # 1 , a signal B transmitted from the antenna # 2 in the mobile station # 1 , a signal C transmitted from the antenna # 1 in the mobile station # 2 , and a signal D transmitted from the antenna # 2 in the mobile station # 2 are mutually orthogonal.
  • the base station can allocate orthogonal radio resources in the time, frequency, or code domain. This resource allocation can reduce multiple-access interference.
  • FIG. 15 shows a block diagram of a base station 30 in accordance with a fourth embodiment of the present invention.
  • the fourth embodiment an approach for orthogonalizing signals from respective antennas in the time domain in addition to orthogonalizing signals from respective mobile stations in the time domain is described below.
  • the base station 30 includes received signal modulation units 301 - 11 through 301 - 32 , reception timing detecting units 303 - 11 through 303 - 32 , control information generating units 307 - 11 through 307 - 32 , and transmission signal generating units 309 - 11 through 309 - 32 for each antenna.
  • the base station 30 further includes a transmission timing determining unit 305 and a radio resource allocating unit 313 .
  • the received signal modulation units 301 - 11 through 301 - 32 modulate signals received from the mobile stations at the respective antennas.
  • the reception timing detecting units 303 - 11 through 303 - 32 detect reception timings of the received signals and provide reception timing information to the transmission timing determining unit 305 .
  • the transmission timing determining unit 305 measures a reception timing difference based on reception timing information for each antenna in each mobile station within all sectors in the base station.
  • the transmission timing determining unit 305 calculates transmission timings so that signals transmitted from the respective antennas in the respective mobile stations are synchronized within a guard interval.
  • the radio resource allocating unit 313 generates radio resource allocation information for each mobile station so that signals transmitted from the respective antennas in the respective mobile stations are orthogonal in the time domain.
  • the control information generating units 307 - 11 through 307 - 32 generate transmission timing control information for the corresponding mobile stations based on the calculated transmission timings and the radio resource allocation information.
  • the transmission signal generating units 309 - 11 through 309 - 32 generate transmission signals for the corresponding mobile stations. The corresponding transmission signal is transmitted to each mobile station.
  • FIG. 16 shows a diagram illustrating how signals from the respective antennas are orthogonal at the base station in the time domain in addition to how signals from the respective mobile stations are orthogonal at the base station in the time domain.
  • pilot channels from the respective antennas in the mobile station # 1 or # 2 can be orthogonalized in the time domain. As mentioned above, timing errors may occur within guard intervals (CPs).
  • the pilot channels orthogonalized among the respective antennas in the time domain can be further orthogonalized among the mobile stations # 1 and # 2 in the time domain. Consequently, the four pilot channels from the two antennas in the mobile station # 1 and the two antennas in the mobile station # 2 do not interfere with each other on the time axis. Therefore, interference from the respective antennas can be reduced in MIMO transmission, and thus communication quality can be improved.
  • FIG. 17 shows a block diagram of a mobile station 40 communicating with the base station 30 .
  • the mobile station 40 includes pilot channel generating units 401 - 1 through 401 - 2 , data channel generating units 403 - 1 through 403 - 2 (as used herein, the data channel generating units 403 - 1 through 403 - 2 include the capability of generating a control channel), channel multiplexing units 405 - 1 through 405 - 2 , scrambling code multiplying units 407 - 1 through 407 - 2 , and transmission timing adjusting units 409 - 1 through 409 - 2 for each antenna. These units act in the same way as the units shown in FIGS. 7 , 9 , and 11 .
  • the mobile station 40 further includes a control unit 411 for providing transmission timing control information received from the base station to the transmission timing adjusting units 409 - 1 through 409 - 2 (code allocation information and frequency allocation information in FIG. 17 are described below). Specifically, the control unit 411 receives transmission timing control information from the base station and distributes the transmission timing control information to the transmission timing adjusting units 409 - 1 through 409 - 2 for the respective antennas, so that the signals received at the base station are orthogonal in the time domain.
  • a base station 30 in accordance with the fifth embodiment can be arranged as shown in FIG. 15 .
  • the transmission timing determining unit 305 determines transmission timings so that pilot channels are orthogonal among the mobile stations in the time domain.
  • the radio resource allocating unit 313 generates code allocation information for each mobile station so that pilot channels are orthogonal among the antennas in the code domain.
  • the code allocation information is transmitted from the transmission signal generating units 309 - 11 through 309 - 32 to each mobile station.
  • FIG. 18 shows a diagram illustrating how signals from the respective antennas are orthogonal at the base station in the code domain in addition to how signals from the respective mobile stations are orthogonal at the base station in the time domain.
  • pilot channels from the respective antennas in the mobile station # 1 or # 2 can be orthogonalized in the code domain.
  • the pilot channels orthogonalized among the respective antennas in the code domain can be further orthogonalized among the mobile stations # 1 and # 2 in the time domain. Consequently, the four pilot channels from the two antennas in the mobile station # 1 and the two antennas in the mobile station # 2 do not interfere with each other.
  • pilot channels among the mobile stations do not interfere with each other on the time axis as shown in FIG. 18(B)
  • pilot channels among the antennas do not interfere with each other in the code domain as shown in FIG. 18(C) .
  • the control unit 411 in the mobile station 40 receives code allocation information generated by the radio resource allocating unit 313 in the base station 30 , in addition to transmission timing control information from the base station 30 .
  • the control unit 411 distributes the code allocation information to the pilot channel generating units 401 - 1 through 401 - 2 for the respective antennas, so that the signals received at the base station are orthogonal among the antennas in the code domain.
  • the control unit 411 further distributes the transmission timing control information to the transmission timing adjusting units 409 - 1 through 409 - 2 for the respective antennas, so that the signals received at the base station are orthogonal among the mobile stations in the time domain.
  • a base station 30 in accordance with the sixth embodiment can be arranged as shown in FIG. 15 .
  • the transmission timing determining unit 305 determines transmission timings so that pilot channels are orthogonal among the mobile stations in the time domain.
  • the radio resource allocating unit 313 generates frequency allocation information for each mobile station so that pilot channels are orthogonal among the antennas in the frequency domain.
  • the frequency allocation information is transmitted from the transmission signal generating units 309 - 11 through 309 - 32 to each mobile station.
  • FIG. 19 shows a diagram illustrating how signals from the respective antennas are orthogonal at the base station in the frequency domain in addition to how signals from the respective mobile stations are orthogonal at the base station in the time domain.
  • pilot channels from the respective antennas in the mobile station # 1 or # 2 can be orthogonalized in the frequency domain.
  • the pilot channels orthogonalized among the respective antennas in the frequency domain can be further orthogonalized among the mobile stations # 1 and # 2 in the time domain. Consequently, the four pilot channels from the two antennas in the mobile station # 1 and the two antennas in the mobile station # 2 do not interfere with each other.
  • pilot channels among the mobile stations do not interfere with each other on the time axis as shown in FIG. 19(B)
  • pilot channels among the antennas do not interfere with each other in the frequency domain as shown in FIGS. 19(C) and (D).
  • the control unit 411 in the mobile station 40 receives frequency allocation information generated by the radio resource allocating unit 313 in the base station 30 , in addition to transmission timing control information from the base station 30 .
  • the control unit 411 distributes the frequency allocation information to the pilot channel generating units 401 - 1 through 401 - 2 for the respective antennas, so that the signals received at the base station are orthogonal among the antennas in the frequency domain.
  • the control unit 411 further distributes the transmission timing control information to the transmission timing adjusting units 409 - 1 through 409 - 2 for the respective antennas, so that the signals received at the base station are orthogonal among the mobile stations in the time domain.
  • a base station 30 in accordance with the seventh embodiment can be arranged as shown in FIG. 15 .
  • the transmission timing determining unit 305 determines transmission timings so that pilot channels are orthogonal among the antennas in the time domain.
  • the radio resource allocating unit 313 generates code allocation information for each mobile station so that pilot channels are orthogonal among the mobile stations in the code domain.
  • the code allocation information is transmitted from the transmission signal generating units 309 - 11 through 309 - 32 to each mobile station.
  • FIG. 20 shows a diagram illustrating how signals from the respective antennas are orthogonal at the base station in the time domain in addition to how signals from the respective mobile stations are orthogonal at the base station in the code domain.
  • the pilot channels orthogonalized among the respective antennas in the time domain can be orthogonalized among the mobile stations # 1 and # 2 in the code domain. Consequently, pilot channels among the antennas do not interfere with each other on the time axis as shown in FIG. 20(A) , and pilot channels among the mobile stations do not interfere with each other in the code domain as shown in FIG. 20(B) .
  • the control unit 411 in the mobile station 40 receives code allocation information generated by the radio resource allocating unit 313 in the base station 30 , in addition to transmission timing control information from the base station 30 .
  • the control unit 411 distributes the code allocation information to the pilot channel generating units 401 - 1 through 401 - 2 for the respective antennas, so that the signals received at the base station are orthogonal among the mobile stations in the code domain.
  • the control unit 411 further distributes the transmission timing control information to the transmission timing adjusting units 409 - 1 through 409 - 2 for the respective antennas, so that the signals received at the base station are orthogonal among the antennas in the time domain.
  • a base station 30 in accordance with the eighth embodiment can be arranged as shown in FIG. 15 .
  • the radio resource allocating unit 313 generates code allocation information for each mobile station so that pilot channels are orthogonal both among the mobile stations and among the antennas in the code domain.
  • the code allocation information is transmitted from the transmission signal generating units 309 - 11 through 309 - 32 to each mobile station.
  • FIG. 21 shows a diagram illustrating how signals from the respective antennas are orthogonal at the base station in the code domain in addition to how signals from the respective mobile stations are orthogonal at the base station in the code domain.
  • the pilot channels from the respective antennas in the mobile stations # 1 and # 2 can be orthogonalized with each other in the code domain. Consequently, pilot channels both among the base stations and among the antennas do not interfere with each other in the code domain as shown in FIG. 21(B) .
  • the control unit 411 in the mobile station 40 receives code allocation information generated by the radio resource allocating unit 313 in the base station 30 .
  • the control unit 411 distributes the code allocation information to the pilot channel generating units 401 - 1 through 401 - 2 for the respective antennas, so that the signals received at the base station are orthogonal both among the mobile stations and among the antennas in the code domain.
  • a base station 30 in accordance with the ninth embodiment can be arranged as shown in FIG. 15 .
  • the radio resource allocating unit 313 generates code allocation information and frequency allocation information for each mobile station, so that pilot channels are orthogonal among the mobile stations in the code domain and are orthogonal among the antennas in the frequency domain.
  • the code allocation information and the frequency allocation information are transmitted from the transmission signal generating units 309 - 11 through 309 - 32 to each mobile station.
  • FIG. 22 shows a diagram illustrating how signals from the respective antennas are orthogonal at the base station in the frequency domain in addition to how signals from the respective mobile stations are orthogonal at the base station in the code domain.
  • the pilot channels orthogonalized among the respective mobile stations # 1 and # 2 in the code domain can be orthogonalized among the antennas in the frequency domain. Consequently, pilot channels among the mobile stations do not interfere with each other in the code domain, and pilot channels among the antennas do not interfere with each other in the frequency domain, as shown in FIG. 22(B) and FIG. 22(C) .
  • the control unit 411 in the mobile station 40 receives code allocation information and frequency allocation information generated by the radio resource allocating unit 313 in the base station 30 .
  • the control unit 411 distributes the code allocation information and the frequency allocation information to the pilot channel generating units 401 - 1 through 401 - 2 for the respective antennas, so that the signals received at the base station are orthogonal among the mobile stations in the code domain and are orthogonal among the antennas in the frequency domain.
  • a base station 30 in accordance with the tenth embodiment can be arranged as shown in FIG. 15 .
  • the transmission timing determining unit 305 determines transmission timings so that pilot channels are orthogonal among the antennas in the time domain.
  • the radio resource allocating unit 313 generates frequency allocation information for each mobile station so that pilot channels are orthogonal among the mobile stations in the frequency domain.
  • the frequency allocation information is transmitted from the transmission signal generating units 309 - 11 through 309 - 32 to each mobile station.
  • FIG. 23 shows a diagram illustrating how signals from the respective antennas are orthogonal at the base station in the time domain in addition to how signals from the respective mobile stations are orthogonal at the base station in the frequency domain.
  • the pilot channels orthogonalized among the respective antennas in the time domain can be orthogonalized among the mobile stations # 1 and # 2 in the frequency domain. Consequently, pilot channels among the antennas do not interfere with each other on the time axis, and pilot channels among the mobile stations do not interfere with each other in the frequency domain as shown in FIG. 23(B) and FIG. 23(C) .
  • the control unit 411 in the mobile station 40 receives frequency allocation information generated by the radio resource allocating unit 313 in the base station 30 , in addition to transmission timing control information from the base station 30 .
  • the control unit 411 distributes the frequency allocation information to the pilot channel generating units 401 - 1 through 401 - 2 for the respective antennas, so that the signals received at the base station are orthogonal among the mobile stations in the frequency domain.
  • the control unit 411 further distributes the transmission timing control information to the transmission timing adjusting units 409 - 1 through 409 - 2 for the respective antennas, so that the signals received at the base station are orthogonal among the antennas in the time domain.
  • a base station 30 in accordance with the eleventh embodiment can be arranged as shown in FIG. 15 .
  • the radio resource allocating unit 313 generates frequency allocation information and code allocation information for each mobile station, so that pilot channels are orthogonal among the mobile stations in the frequency domain and are orthogonal among the antennas in the code domain.
  • the frequency allocation information and the code allocation information are transmitted from the transmission signal generating units 309 - 11 through 309 - 32 to each mobile station.
  • FIG. 24 shows a diagram illustrating how signals from the respective antennas are orthogonal at the base station in the code domain in addition to how signals from the respective mobile stations are orthogonal at the base station in the frequency domain.
  • the pilot channels orthogonalized among the respective mobile stations # 1 and # 2 in the frequency domain can be orthogonalized among the antennas in the code domain. Consequently, pilot channels among the mobile stations do not interfere with each other in the frequency domain, and pilot channels among the antennas do not interfere with each other in the code domain, as shown in FIG. 24(B) and FIG. 24(C) .
  • the control unit 411 in the mobile station 40 receives frequency allocation information and code allocation information generated by the radio resource allocating unit 313 in the base station 30 .
  • the control unit 411 distributes the frequency allocation information and the code allocation information to the pilot channel generating units 401 - 1 through 401 - 2 for the respective antennas, so that the signals received at the base station are orthogonal among the mobile stations in the frequency domain and are orthogonal among the antennas in the code domain.
  • a base station 30 in accordance with the twelfth embodiment can be arranged as shown in FIG. 15 .
  • the radio resource allocating unit 313 generates frequency allocation information for each mobile station so that pilot channels are orthogonal both among the mobile stations and among the antennas in the frequency domain.
  • the frequency allocation information is transmitted from the transmission signal generating units 309 - 11 through 309 - 32 to each mobile station.
  • FIG. 25 shows a diagram illustrating how signals from the respective antennas are orthogonal at the base station in the frequency domain in addition to how signals from the respective mobile stations are orthogonal at the base station in the frequency domain.
  • the pilot channels from the respective antennas in the mobile stations # 1 and # 2 can be orthogonalized with each other in the frequency domain. Consequently, pilot channels both among the base stations and among the antennas do not interfere with each other in the frequency domain as shown in FIG. 25(B) and FIG. 25(C) .
  • the control unit 411 in the mobile station 40 receives frequency allocation information generated by the radio resource allocating unit 313 in the base station 30 .
  • the control unit 411 distributes the frequency allocation information to the pilot channel generating units 401 - 1 through 401 - 2 for the respective antennas, so that the signals received at the base station are orthogonal both among the mobile stations and among the antennas in the frequency domain.
  • the base station allocates orthogonal radio resources to mobile stations within all sectors, in order to reduce interference with signals from the mobile station # 3 which is situated in the sector boundary.
  • the base station may allocate an orthogonal pilot sequence (a radio resource orthogonal to that for the other mobile stations) which is different from the orthogonal pilot sequence for the other mobile stations (mobile stations # 1 , # 2 , # 4 , # 5 ) to only the mobile station # 3 which is situated in the sector boundary (near the overlapping region among sectors). Because there is little likelihood that the mobile stations far from the sector boundary move to the other sectors, the base station may allocate the same orthogonal pilot sequence to the mobile stations # 1 and # 4 (or the mobile stations # 2 and # 5 ).
US12/064,541 2005-08-23 2006-08-21 Base station and communication system Expired - Fee Related US7912030B2 (en)

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KR20080036224A (ko) 2008-04-25
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TW200718233A (en) 2007-05-01
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KR101179160B1 (ko) 2012-09-03
US20090135791A1 (en) 2009-05-28
JP4202355B2 (ja) 2008-12-24
EP1919232A1 (fr) 2008-05-07
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JP2007089108A (ja) 2007-04-05
WO2007023767A1 (fr) 2007-03-01

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